1. Field of the Invention
The present invention relates in general to a method for detecting creep swelling in tubular members, and, in particular, to an ultrasonic method for detecting creep swelling in fossil utility steam lines and headers.
2. Description of the Related Art
The current method for detecting creep swelling in fossil utility steam lines and headers requires tedious mechanical measurements with a large caliper. The outside diameter of the pipe is measured rather than the circumference and so more than one measurement is required at a single location in order to check for out of roundness. As a result, the method is slow and the results are highly operator dependent. Additionally, the present method requires removal of insulation which can be very time consuming.
Other methods employed are based upon operational history and also plastic replication of material microstructure. Each technique has its own associated limitations and thus it is desirable to have several approaches to predict remaining lifetime.
The necessity for inspections is evidenced by reported steam line failures at power plants. The unanticipated failures of these components are potentially catastrophic to the plant operation as well as plant personnel and even may cause extensive damage to adjacent equipment.
Particular problems in inspecting arise when the pipes are composed in many short lengths with associated bends, wyes (y's), and tees (t's). This inaccessability problem is also increased with the presence of radiographic plugs, hangers and support systems.
Thus, there is a need for a rapid method for detecting creep swelling in fossil utility steam lines and headers. The method should require very little insulation removal and be suitable to scanning or acquiring close data points along the pipe or header in order to efficiently locate regions of creep swelling.